You're going to want your wellies for this one! Event time 19:30-20:00
I've promised for a while to set up an event in the dark, so here it is - a social chat just inside the entrance to the former Brecon and Merthyr (or Breakneck and Murder!) rail tunnel at Torpantau in the Brecon Beacons - the highest tunnel built on the UK rail network.
Limited parking is available at the trailhead (but don't block access to the forest track) or in the waypointed car park slightly further away.
Note: Your participation in this event is at your own risk, I make no assertion as to the safety of the tunnel, but I have visited many times without incident, as do many members of the public and outdoor centre groups. It's your choice whether or not to follow. I'm not saying no under 18s, but it's at your own judgement and for legal reasons they must be accompanied by a parent.
Whilst the place was originally engineered for human passage (on trains), it's been about 7 years since a formal inspection has taken place and published by a qualified person; there is always a slight risk of falling bits of rock or more likely brickwork, so you may wish to wear a helmet - you can pick up builders helmets in places where you might want to 'fix things with screws' perhaps, and similar places, with change from a fiver.
After the event you may wish to complete the full walk of the length of the tunnel - as it's got quite a curve there is a complete absence of light in the middle - so you'll probably want a torch!